This disclosure relates to a drivable working machine, particularly a truck-mounted concrete pump, comprising a vehicle, a concrete placing boom, which can be rotated on a vehicle-fixed carrying structure by means of a slewing gear, and a plurality of supporting legs arranged on the carrying structure for supporting the carrying structure in a working position. This disclosure further relates to a method for the low-oscillation operation of such a drivable working machine.
In the case of drivable concrete pumps of the type described in DE 102 46 447 A1, the carrying structure is placed onto the undercarriage of a truck chassis. The boom pedestal or slewing gear of the carrying structure forms the interface between the placing boom and the supporting legs. The torque load caused by the placing boom is distributed among the supporting legs via the boom pedestal and is applied to the base surface. In the case of drivable concrete pumps, a carrying structure that is equipped with two telescoping supporting legs in the front and two supporting legs that can be swung out in the rear is especially preferred. Because components are increasingly of light-weight design, oscillations are an ever greater problem. In addition to the boom motions, disturbance torques are caused by the motions of the conveying pump and the redirecting of the concrete flow. A disadvantage here is that the rear structure protrudes far rearward with the feed hopper. In the working position, the hydraulic cylinders of the working legs are generally extended on both sides. Previously, the hydraulic cylinders were first locked by means of a so-called alternating operation valve before the hydraulic supply was switched over to the placing boom. In order to avoid tipping, the vehicle wheels should not have ground contact but rather should be lifted off by means of the supporting legs. However, the yaw stiffness is lowest in this arrangement. Yaw motions are promoted by the play in the supporting legs and the long flexural structure of the supporting legs, which acts as a torsion beam.